An ability of communication terminal equipment such as a cellular phone terminal for performing communication by radio anywhere in the world, i.e., ubiquitous coverage, is not realistic today but is now under development.
According to Earl McCune, “High-Efficiency, Multi-Mode, Multi-Band Terminal Power Amplifiers”, IEEE microwave magazine, March 2005, PP. 44 to 55, these mobile systems include cellulars of GSM (Global System for Mobile Communication), GPRS (General Packet Radio Service), EDGE (Enhanced Data for GSM Evolution; Enhanced Data for GPRS), and WCDMA (Wideband Code Division Multiple Access), networks such as IEEE 803.11-b, -a, -g, and the like, and personal area networks such as Bluetooth and ZigBee. Characteristics of these systems cover a wide range of combinations of signals of a fixed envelope and an envelope change, multiplexes of time division and code division, and a transmission power ranging from high (several watts) to low (microwatts). As a result, there are increasing demands for RF power amplifiers applicable to a multimode.
On the other hand, in Shuyun Zhang et al, “A Novel Power-Amplifier Module for Quad-Band Wireless Handset Applications”, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 52, No. 11, NOVEMBER 2003, PP. 2203 TO 2210, an RF power amplifier module that transmits a quad-band including frequency bands of GSM850, GSM900, DCS1800, and PCS1900 is described. DCS is the abbreviation of Digital Cellular System and PCS is the abbreviation of Personal Communication System. This RF power amplifier module includes a first power amplifier that amplifies a first RF transmission input signal having a first frequency band of GSM850 and GSM900 and a second power amplifier that amplifies a second RF transmission input signal having a second frequency band of DCS1800 and PCS1900.
In the communication in GSM850, GSM900, DCS1800, and PCS1900, the TDMA system that is capable of setting each of plural time slots in any one of an idle state, an operation for reception from a base station, and an operation for transmission to the base station in a time division manner is adopted. TDMA is the abbreviation of Time-Division Multiple Access. As one type of the TDMA system, the GSM system is known in which only the phase modulation is used. A system for improving a communication data transfer rate compared with the GSM system is also known. As this improved system, an EDGE system in which the amplitude modulation is used together with the phase modulation also attracts attention recently.
The WCDMA system in which a communication data transfer rate is improved by using the amplitude modulation together with the phase modulation as in the EDGE system also attracts attention. In this WCDMA system, rather than the TDMA system, the frequency division CDMA system in which a frequency of 2110 MHz to 2170 MHz is used for an operation for reception from a base station and, on the other hand, a frequency of 1920 MHz to 1980 MHz is used for an operation for transmission to the base station is adopted. CDMA is the abbreviation of Code Division Multiple Access.
In Gary Hau et al, “High Efficiency, Wide Dynamic Range Variable Gain and Power Amplifier MMICs for Wide-Band CDMA Handsets”, IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 11, No. 1, JANUARY 2001, PP. 13 to 15, since a wide control range and high linearity are required in power control of an RF power amplifier of the WCDMA system, a variable gain amplifier formed by a variable attenuator is connected to an input of the RF power amplifier.
In JP-A-2001-168647, in order to cause an RF power amplifier to cope with a maximum power of 36 dBm of GSM (a nonlinear operation) and a maximum power of 29 dBm of EDGE (a linear operation), a gain control voltage is applied to a first gain close to a drain of a dual-gate field effect transistor and a bias voltage, which is obtained by dividing the gain control voltage with a voltage divider controlled by a mode switch, and an RF input signal are applied to a second gate close to a source. In a mode of GSM of the nonlinear operation, the mode switch is controlled to be on and a shallow bias voltage generated by the divided bias voltage is applied to the second gate. In a mode of EDGE of the nonlinear operation, the mode switch is controlled to be off and a deep bias voltage generated by the gain control voltage not divided is applied to the second gate. U.S. Pat. No. 6,443,639 corresponds to this patent document.
In Elliot R. Brown, “RF-MEMS Switches for Reconfigurable Integrated Circuits”, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 46, NO. 11, NOVEMBER 1998, PP. 1868 to 1880 (hereinafter referred to as Non-Patent Document 4), an RF-MEMS switch based on MEMS (Micro Electro-Mechanical System) is introduced. It is reported that this switch shows an excellent high-frequency characteristic and is designed and manufactured by a technique similar to VLSI.